Mosfet Question (Trace Elliot)

[sweatyk]

I think I had found the culprit. I case you don't remember this was the Trace Elliot GP12SMX that I thought I was have an output issue with. I reassembled the entire amp. And amazingly if worked beautifully.........this doesn't pass the sniff test if you know what I mean. When I installed the front face plate and then tried it the signal was week and a disturbing hum was present. It would adjust up and down with the output level. I disassembled it again removing the preamp PCB and proceeded to remove all pots and clean and lube via complete dis-assembly. My previous lube job got a little messy on the PCB and I was not happy with that. After I had cleaned and lubed them all I scoured over the PCB once again with my magnifying glass and something caught my eye. I had looked dozens of times but I caught from another angle. There was a solder pad with a hairline crack on the neg. side of a 2200uf @ 63V cap. Tried to identify it on the schematic but gave up. This was the issue causing the failure. The amp sounds as it is suppose to now.

Not being a seasoned tech like most I sometimes follow what seems correct but not the best practice as pointed out to me. Somehow I do manage to get it resolved but it might take me a little longer. Probably faster if I followed you guys more but I’m old and stubborn that way. I’m posting this to bring closure to this thread. Glad I don’t do this for a living…….I would be skinny.

[olddawg]

That would be a main rail power supply filter cap. If disconnected you would get a hilatious hum. It's a common failure in many SS amps. They are fairly large and tend to vibrate loose. 2200uf, 4700uf, etc. first place to look with a hum and no DC offset on the output. There are probably two, one for each rail voltage. Resolder them both.